Upon payment of the purchase price the Secretary of the Interior is authorized by appropriate patent to convey all the right, title, and interest in and to said lands to the purchaser at said sale, subject, however, to such reservations, limitations, or conditions as said Secretary may deem proper: Provided, That not over one hundred and sixty acres shall be sold to any one person: Provided further, That any patent issued hereunder shall contain a reservation to the United States of all oil, gas, coal, and other mineral.